Formation and chemistry of radical anions in the gas phase

Abstract

The research concerned with the ion/molecule chemistry of radical anions is reviewed together with the thermochemical properties of these ions and the related neutral species. Attention has been given to the formation of radical anions in the gas phase by various pathways, such as (dissociative) electron attachment and bimolecular reactions. A brief discussion of the electron affinity of the neutral species related to a given radical anion has been included, because this parameter is important for the discussion of the finding that an HA˙ radical is often more acidic than the related H2A molecule. In addition, the thermochemical properties form the basis for a discussion of the various processes that may occur in reactions of radical anions with organic molecules. In particular, electron transfer, proton transfer, and hydrogen atom abstraction reactions have been described for selected radical anions. Other processes that have been reviewed include SN2 substitution and an attack on a carbonyl function in an organic molecule. The interplay between these latter two processes has been described for the reactions of some halogen-substituted carbene radical anions with the methyl ester of trifluoroacetic acid and dimethyl carbonate. The structural characterization of radical anions, distonic radical anions in particular, is summarized with an emphasis on methods such as isomer-specific ion/molecule reactions and collision-induced dissociation or charge-reversal processes. © 1998 John Wiley & Sons, Inc., Mass Spectrom Rev 16, 181–200, 1997